The US also has rule of law, a bill of rights, and government checks and balances designed to try to limit how much damage government corruption can do. While it can (and probably does) infringe on people's rights in many situations, these are not carried out at the same scale as in China. The free press and freedom of speech (and communication) means that if it were occurring on any significant scale, you would hear about it. Many people are outraged by Guantanamo Bay, and rightfully so.
Meanwhile, in China, no one even knows about similar or worse abuses even at a much larger scale. And with tighter control of the Internet, adding SSL spoofing to DNS hijacking, GFW monitoring and filtering at egresses, the vast majority of the populace never will.*
* While there remain ways around this (VPNs, for example), those just act as an escape valve for nerd outrage; the majority of people don't understand the problem well enough to care, and will never go to any effort to reach beyond that convenient (filtered) local news source and (monitored) local email, VOIP (special version of Skype for China, folks), chat rooms, SMS (now openly monitored by the phone company "for porn"), etc.